This is awesome! I mean, it sucks that it has to run in Rosetta, but I can enter my own units and types of measurement! I've been looking for a unit converter that wouldn't annoy the hell out of me (I'm a theoretical physicist, so I deal with some pretty arcane units) and I think I just found it. Please LOS, please, at least make it universal. I don't know that there is much more to do to improve it after that, but the slow startup time may be an issue for me when I could just do it myself with some paper.

@ starbuck65:
No longer supported or developed, but... it still works.
And, although it is a PowerPC application, developed in the ages of Mac OS X 10.1, it works very well under Leopard in my Intel iMac.
And so does Perfect Pitch, a guitar tuner from the same developer(s).